An antenna assembly whose antenna operates effectively, regardless of the location/environment where the assembly is placed, is referred to as placement-immune. By building an antenna on a substrate of magnetic conductor material, the radiated field will be positively reinforced in the desired radiation direction instead of being negatively affected by the environment. This approach, which has been discussed thoroughly in theoretical research, presents a difficult problem, namely, how to build magnetic conductor materials necessary for in-phase field reflections without requiring substantially thick substrates at low frequencies.
The magnetic conductor substrate must be carefully designed to suit the antenna's frequency dependent needs. Such a substrate is also referred to herein as an artificial magnetic conductor (AMC) substrate, or simply an AMC. AMCs have been created with internal electrically conductive metal components (metal inclusions) to create inductor-capacitor based surface resonances for in-phase reflection of electromagnetic waves. These metal inclusions limit the minimal thickness of the substrate. Sievenpiper style high-impedance surfaces have been used to artificially create magnetic conductors at specific frequencies by making an open circuit boundary condition on the surface of a substrate for incoming electromagnetic waves. The Sievenpiper AMC requires via holes and capacitive patches above a ground plane to act as resonant inductor-capacitor circuits, and its minimal thickness is limited by the interior metal required to create the resonant circuits. Other types of AMCs have been produced by embedding curved metal strips into dielectrics such that the metal strips create resonant inductor-capacitor circuits.
It is desirable in view of the foregoing to provide for an AMC that is thinner and more flexible than conventional AMCs.